The normal clearance between the brake pad(s) or brake block(s) and the disc or drum or wheel frictionally engageable thereby, generally increases with progressive wear of the pad(s) or block(s) that arises from repeated brake applications. This clearance increase or "slack" must be traversed before the brakes can be applied. With so-called "slack adjusters" currently in use the total stroke of the device is measured, i.e., the sum of the normal clearance plus the deflection of the rigging mounting components of the brake. When this total stroke as measured becomes too great, it is reduced by a predetermined fixed amount. This precludes the use of such "slack adjusters" where very small clearances are required.